The present invention is directed to a method of scanning silver-halide-containing color photographic and photothermographic film. In particular, the present invention comprises record shifting by means by employing at least one infrared dye in a color unit of the film, thereby forming at least one image record in the infrared region.
It has become desirable to limit the amount of solvent or processing chemicals used in the processing of silver-halide films. A traditional photographic processing scheme for color film involves development, fixing, bleaching, and washing, each step typically involving immersion in a tank holding the necessary chemical solution. Images are then produced by optical printing. By scanning the film image following development, the subsequent processing solutions could be eliminated for the purposes of obtaining a color image. Instead, the scanned image could be used to directly provide the final image to the consumer.
By the use of photothermographic film, it would be possible to eliminate processing solutions altogether, or alternatively, to minimize the amount of processing solutions and the complex chemicals contained therein. A photothermographic (PTG) film by definition is a film that requires energy, typically heat, to effectuate development. A dry PTG film requires only heat; a solution-minimized PTG film may require small amounts of aqueous alkaline solution to effectuate development, which amounts may be only that required to swell the film without excess solution. Development is the process whereby silver ion is reduced to metallic silver and, in a color system, a dye is created in an image-wise fashion.
In PTG films, the silver metal and silver halide is typically retained in the coating after the heat development. It can be difficult to scan through imagewise exposed and photochemically processed silver-halide films when the undeveloped silver halide is not removed from the film during processing. The retained silver halide is reflective, and this reflectivity appears as density in a scanner. The retained silver halide scatters light, decreasing sharpness and raising the overall density of the film, to the point in high-silver films of making the film unsuitable for scanning. High densities result in the introduction of Poisson noise into the electronic form of the scanned image, and this in turn results in decreased image quality. Furthermore, the retained silver halide can form non-image density in reaction to ambient/viewing/scanning light, rendering non-imagewise density, degrading signal-to noise of the original scene, and raising density even higher.
It is therefore an object of the present invention to improve the scanning of photothermographic film without removing the silver halide and/or metallic silver, or partially removing the same.
It has been found that the reflectivity of retained silver halide is quite dependent on wavelength and that blue light is more reflected than green light which in turn is more reflected than red light which in turn is more reflected than infrared light. Accordingly, it has been found that the expedient of forming at least one image record in the infrared leads to the formation of high quality images.
In one embodiment of the invention, record shifting is accomplished by providing a light-sensitive color element having a blue light-sensitive layer unit having a magenta dye forming coupler, a green light-sensitive layer having a cyan dye forming coupler, and a red light-sensitive layer having an infrared dye forming coupler.